"The nice part," she says, "is I come to the judges' table with experience in the exact realm that I'm looking at. So, I have a lot of empathy and understanding for the folks on stage. There's a lot of love there.

"I'm a fan, first and foremost, so it's really nice to be able to give constructive criticism, and it's all in the name of helping them improve."

On Monday, Sept. 19, "The Sing-Off" launches for the first time in the fall, after having short runs in December in 2009 and 2010, and the time slot puts it directly against another top competition show, ABC's "Dancing With the Stars."

"That's why they make DVRs!" Bareilles says.As to what she loves about a cappella singing, in which the human voice is the only instrument, Bareilles says, "I loved what I think a lot of these groups love, which is the camaraderie of it. It's being part of a unit.

"There's something -- this might sound a little cheesy -- there's something primal about it. People have been singing together in groups since the beginning of time. There's a real brotherhood that seems to happen with a cappella singing, naturally. It's a really sacred space, sharing music with your friends.

"For me, in college, that's where I felt I found my first really true friends who understood me as a total music nerd, and we could all be little outcasts together."And, she says, as a bonus, "It's very cheap."

Favorite book: "That's a tough one, because it's changed. When I was a little girl, it was 'The Secret Garden' and 'Black Beauty.' I read both of those over and over again. As an adult, the book that's really spoken to me recently is 'Eat, Pray, Love' by Elizabeth Gilbert. I did not care for the movie, however, because I loved the book so much."

Favorite movie: " 'Princess Bride.' I think it's timeless. It's a wonderful balance of a fantasy film that has heart, and I can watch it anytime, any day, any place. It never seems to go out of style. It's so well-done and well-written, and the cast is amazing, of course."

Favorite music: "This changes for me all the time. Right now, in my car I'm listening to Ben Folds. He's one of my favorites. I love piano pop. I love Billy Joel, Elton John. If I had to choose a genre, for me, it would be pop music. But I'm more of an old-school pop music, so as I said, Billy Joel, Elton John, Carole King, Joni Mitchell, that kind of stuff."